The invention relates generally to air filters and, more particularly, to expandable air filters for use in furnaces.
The use of disposable air filters in the air distribution system of a building has provided an efficient and economical method of removing undesirable particulate matter from the air. In its simplest form, a rectangular piece of filter media material is mounted in a cardboard framework, with the combination then being mounted in a filter cabinet or an air duct somewhere in the air distribution system. With a hot air furnace, it is common practice to place the filter in a filter cabinet just upstream of the fan so as to filter the return air as it enters the furnace from the return air duct. When the filter is spent, i.e. when it has collected a sufficient amount of particulate matter as to be considered xe2x80x9cfullxe2x80x9d, then it is removed and replaced with a new filter.
One way to increase the surface area of a filter is to make it multi-dimensional, with a plurality of accordion-like pleats. Such a pleated media filter is thicker than a non pleated filter and therefore provides more active surface area, making it more effective and longer lasting. It can be rechargeable, i.e. cleanable, or disposable depending primarily on the type of material used for the filter media. A disposable material, however, tends to be less durable and strong, and many such materials will not be suitable for providing the necessary support structure that is necessary to secure and maintain the installed position of the disposable portion of the filter in the nondisposable support framework. Further, a homeowner should be able to simply and easily remove, replace and dispose of a dirty filter.
It would also be desirable for a serviceperson to have a single sized filter which can be used to accommodate various sizes of cabinet openings, such that his inventory can be substantially reduced to. Generally there are three sizes of filters that must be stocked and carried in order to meet the various installation requirements.
A pleated filter element may be selectively collapsed for storage and shipping purposes and then later expanded for installation and use. To accomplish this, it is necessary to provide some means to maintain the filter element in its expanded condition. It is also desirable to maintain substantially uniform spacing and angling of the pleats, and a comb-like, rigid framework has been used for that purpose.
It is therefore on object of the present invention to provide an improved furnace air filter and method of manufacture. That object and other features and advantages will become more readily apparent upon reference to the following descriptions when taken in conjunction with the appended drawings.
Briefly, in accordance with one aspect of the invention, a plurality of ribbons are placed on either side of the pleated filter element and are secured to the edges of the pleated panels with equal lengths of ribbon portions between the respective pleated panel edges such that, when the filter element is expanded, the expanded ribbon portions cause a uniform spacing and angling of the pleated panels to occur. An end plate is attached to each of the two end filter panels, and the ribbons are expanded and attached to the end plates.
In accordance with another aspect of the invention, the ribbons are secured to the pleated panel edges by way of ultrasonic welding. Such a process provides for an efficient, economical, and effective method of bonding the ribbons to the panel edges.
By yet another aspect of the invention, the filter element is maintained in its expanded condition by a pair of side caps which form the framework for, and to which the two end plates of the filter element are attached. The side caps each have a pair of spaced flanges over which the respective filter element end plates are stretched so as to maintain a minimum expanded length of the filter element, and a pair of bosses engage with corresponding slots in the end plates to hold them in their installed positions.
In accordance with still another aspect of the invention, the end plates, which form part of the disposable portion of the filter, are formed of a plurality of laminated layers which are adhesively bonded and compressed together into a U-shaped structure that provides the necessary strength and rigidity to support the expanded filter in its installed position.
By a further aspect of the invention, the end plates do not form an integral part of the of the disposable filter element and include hanger elements which permit the storage of unexpanded portions of the filter it, such that a single sized filter can be used for multiple sized openings, with the unneeded portions thereof being stored within the end plates.
In the drawings as hereinafter described, a preferred embodiment is depicted; however, various other modifications and alternate constructions can be made thereto without departing from the true spirit and scope of the invention.